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Is this a non-sequiter or just poorly phrased? > Disk galaxies like the Milky Way form stars “inside-out” — starting from the center and working outwards thr
by dotancohen 6mo ago
Is this a non-sequiter or just poorly phrased?
> Disk galaxies like the Milky Way form stars “inside-out” — starting from the center and working outwards through the disk. So, as a general rule, the farther out astronomers look, the younger the stars are.
Do they meant looking out from Earth (which is actually nearer to the center of a spiral arm than to either end) or out from the galactic bulge. Either way doesn't make sense.
- colechristensen 6mo agoIt is beyond obvious what they mean.
- _factor 6mo agoPoorly phrased. The most recent stars are on the edges. The inner stars were first, hence the “working outwards”.
- kakacik 6mo agoBut why? Star forms when enough hydrogen (or maybe also helium) clusters together with gravity to spark fusion IIRC. The center of Milky way ain't some ultra dense place where stars are just trillions of kms from each other to support somehow earlier star formation. Or did ie dark matter/energy somehow coalesce on the outer edge later? Milky way is supposed to be very old place, almost as old as universe itself so one would expect more homogeneous distribution, at least as a layperson.
- Ekaros 6mo agoYou need certain density to start formation progress. Then you get more density as it drags more stuff via gravity from intergalactic void. So new stars form at edges when there is finally enough stuff pulled by gravity of whole galaxy to there for the formation to happen. It seems that you need quite large concentrations(as in scale of whole universe average) to actually get to star formation. Otherwise stars would be uniform trough the universe. Then again I am not astronomer.
- addaon 6mo ago> Then you get more density as it drags more stuff via gravity from intergalactic void. The pre-stellar cloud has the same mass, and thus the same gravitational impact, as the stars that form from it.
- dotancohen 6mo ago> You need certain density to start formation progress. Aren't fluids (such as a hydrogen gas cloud) densest at the bottom of a gravity well? It would be expected that the nearer one is to the galactic center, the denser the intergalactic medium would be.
- layer8 6mo ago[dead]
- malfist 6mo agoWhen does "starting in the center" mean anything besides "starting in the center"? The earth is not the center of the galaxy
- assimpleaspossi 6mo agoHe didn't say that. He said earth is nearer to the center of a spiral arm.
- dylan604 6mo agothe location of earth has precisely zero to do with the topic
- assimpleaspossi 6mo agoAnd your reply has zero to do with what I'm talking about.
- malfist 6mo agoWhat does the center of a spiral arm have to do with the center of the galaxy?
- assimpleaspossi 6mo agoI don't know but that's not what I'm talking about.
- furyofantares 6mo agoThe Earth is where the astronomers are. If they are looking outward (away from the center) then the further they look, the younger the stars.
- happytoexplain 6mo agoI actually am not following what the ambiguity is - stars farther out from the center are younger, no?
- kadoban 6mo agoThe Earth isn't the center of the galaxy, so this feels confusing/confused: > So, as a general rule, the farther out astronomers look, the younger the stars are.
- JumpCrisscross 6mo agoTry: "the farther out [from the center] astronomers look"
- ww520 6mo agoLooking from Earth at the stars closer to the center of a galaxy, they are found to be older. Looking from Earth at the stars closer to the edge of a galaxy, they are found to be younger.
- deleted 6mo ago[deleted]
- eventualcomp 6mo agoTo use an analogy, to add to everybody else: it's like rings on a tree stump. The innermost part of the stump is the oldest; the outer the youngest. Earth is on one of those in-between rings, neither the oldest nor the newest - doesn't matter which of the in-betweens, to be honest. Suppose now that you're an ant on the middle ring of that tree stump. No matter which way you're looking from Earth's middle-ring, either the rings will get gradually older and then younger with increasing distance (if you're looking towards the center-ish), or the rings will get strictly younger (if you're looking away from the center-ish). This analogy obviously breaks down if you delve into details but that should give a better intuition to what's going on.
- furyofantares 6mo agoFrom Earth (where astronomers are) looking "out"ward (away from the bulge).
- jibal 6mo agoEarth isn't relevant. The stars at the center of the galaxy developed first, and development proceeded from the inside out, so the youngest stars are on the edge ... then they get older from there on out, as the stars beyond the edge broke away from the galaxy. The bottom of the age U is the location of the formative edge.
- two_handfuls 6mo agoThey don't mean that the stars migrate out (then further stars would be older), they mean that stars further away from the center start forming later (so further stars are younger). I agree that the phrasing can be confusing.